High frequency receiving antenna



Jan. 109 1961 T. F. THOMPSON HIGH FREQUENCY RECEIVING ANTENNA 2 Sheets-Sheet 1 Filed April 8, 1957 Jan. l0, 1961 T. F. THOMPSON 2,968,037

HIGH FREQUENCY RECEIVING ANTENNA Filed April 8, 1957 2 Sheets-Sheet 2 IN V EN TOR.

Thomas F Thomp son I Y @EQQN genf' HIGH FREQUENCY RECEIVING ANTENNA Thomas F. Thompson, 1465 W. 11th Ave., Eugene, Greg.

Filed Apr. 8, 1957, Ser. No. 651,233

7 Claims. (Cl. 343-701) This invention pertains to antennas, and relates particularly to an improved receiving antenna for television and other high frequency signals.

It is a principal object of the present invention to provide an antenna for receiving television and other high frequency signals of weak strength.

Another important object of this invention is the provision of a television receiving antenna adapted especially for use in fringe areas.

Still another important object of the present invention is to provide a receiving antenna which is adjustable over a relatively wide range of high frequencies.

A still further important object of this invention is to provide a high frequency receiving antenna which is of simplified construction and affords effective operation with a minimum of maintenance and repair.

The foregoing and other objects and advantages of this invention will appear from the following detailed description, taken in connection with the accompanying draw ings, in which:

Figure l is a foreshortened view in side elevation of a receiving antenna embodying the features of the present invention, parts being broken away to disclose details of construction;

Figure 2 is a sectional view taken along the line l2---2 in Figure l;

Figure 3 is a foreshortened view in side elevation of a modified form of receiving antenna embodying the features of the present invention, parts being broken away to disclose details of construction;

Figure 4 is a sectional view taken along the line '4 4 in Figure 3;

Figure 5 is a sectional view taken along the line 5--5 in Figure 3; and

Figure 6 is a schematic diagram of the ystructure shown in Figure l.

The antenna construction illustrated in Figures 1 and 2 is particularly suited to the reception of ultra-high frequency signals, such as the television signals presently allocated to the frequency range of 470 megacycles to 890 megacycles. ln the preferred embodiment illustrated, the antenna includes an elongated outer shell of electrically conductive material, such as aluminum. The shell preferably is formed as two elongated telescoping sections 10, 12, the outer ends of which are removably sealed by caps 14, 16, respectively, made of similar material.

The shell is supported in desired position by mounting post 18. In the embodiment illustrated, the mounting post is hollow and is secured to the inner shell section 10. The outer shell section is provided with a longitudinal slot 20 through which the post projects, thereby orienting the shell sections axially while accommodating longitudinal adjustment therebetween.

2,968,637 Patented Jan. 10, 1961 Positioned within each of the shell sections is an elongated coax cavity member 22 of electrically conducting material, preferably brass and preferably square in cross section. The inward ends of these cavity members are supported in spaced relation with respect to each other and with respect to the outer shell, as by means of the transverse electrically conducting support 24. This support is mounted in frictional contact with the inner shell section for adjustment longitudinally thereof for maintaining the support at the center of the outer shell assembly, and is provided with openings therethrough conforming to the cross section shape of the cavity members, whereby to receive the latter slidably therethrough.

The outer end of each cavity member is substantially closed by a transverse shield 26. A forward projection 28 on the cavity member provides a support for the cylindrical shield 3f) which functions as a housing for the electron discharge tube 32. The shield is secured firmly to the support 28 and to the transverse shield 26, preferably in the oblique position illustrated, as by means of solder.

The electron discharge tube 32 is provided with a plate element 34, a control grid 36, a cathode 38, and a filament 40. The base prong for the plate element projects through an opening 42. in the transverse shield, while the base prongs for the cathode and filament elements are positioned on the outer side of the transverse shield. The control grid lead preferably projects through the top of the electron discharge tube envelope, as illustrated.

The cathode element 38 is connected electrically to projection 26 of the coax cavity member 22 through the parallel combination of resistance 44 and the capacitance 46. One end of the filament element 40 is connected to the coax cavity member through the coil 48, while the opposite end of the filament element is connected through the coil 50 to the filament lead 52. The latter passes through the outward extension 28 of the coax cavity member by means of the feed-through condenser 54.

The plate element 34 of the tube is connected electrically to the outer end of a tuned rod which is positioned within the coax cavity member. This rod is made of electrically conductive material, preferably brass, and also preferably is formed of telescoping sections 56, 58 by which to render the same adjustable in length. The inner telescoping section 58 of the tuned rod is connected to an electrically non-conductive rod 66 such as synthetic plastic, which extends slidably through an electrically non-conductive bearing 62 which is supported by an electrically non-conductive transverse wall 64 secured to the inner end of the coax cavity member.

The plate element 34 of the tube is connected electrically through the tuned rod and coil 66 to the plate lead 68, which extends through the coax cavity member by means of the feed-through condenser '70. An output pickup loop 72 is mounted within the coax cavity member adjacent the tuned rod and is connected to the output coax lead 74.

As indicated in the drawing, the filament, plate and grounded the control grids also are grounded at the 'i points of maximum signal voltage. Thus, amplification of this maximum signal voltage occurs ahead of the source of noise voltage, thereby insuring maximum ratio between signal voltage and noise voltage at the input of a receiver.

It is to be understood of course that the outer shell and tuned rod preferably are rendered adjustable in order to accommodate tuning to desired frequencies within a predetermined range. The overall length of the outer shell preferably is adjusted to half wave length.

In the construction of the antenna described hereinbefore for use on ultra-high frequency television reception, a 6AN4 amplifier tube was moditied to bring the control grid lead through the outer end of the envelope; the resistance 44 was 82 ohms; the condenser 46 was 50 mmf.; the feed-through condenser 54 was 1500 mmf.; the feed-through condenser 70 was 300 mmf.; each of the coils 48, 50 and 66 was formed by twelve turns of No. 22 wire; and the output loop 72 was connected to a 72 ohm coax line 74. Filament voltage was 6.3 volts and plate voltage was 200 volts.

The antenna was installed at a distance of about 100 miles from the UHF transmitting antenna. Excellent snow-free pictures in color and in black and white, and undistorted sound were received even with minimum carrier signal present. For example, it was determined that when even a fraction of a microvolt of signal was fed to the receiver, together with an inherent noise voltage of 4.3 microvolts, completely satisfactory intelligence was obtained.

Referring now to the modification shown in Figures 3, 4 and 5 of the drawings, this antenna is particularly suited for reception of very high frequency signals. The electrically conductive outer shells 80, 82 are provided with removable end caps 84, 86, respectively, and are provided with inward extensions 8S of reduced diameter. These extensions are adapted to be received slidably within a transverse hollow support 90 which is secured to the mounting post 92. An electrically conductive elongated tubing 94, preferably of copper, is supported at its inner end by a transverse electrically non-conductive wall 96, mounted within each of the outer shells. The outer end 98 of the tubing is enlarged in diameter, and closed at its outermost end by a transverse wall 100. An opening is provided in the wall 100 to receive and support therein the cylindrical shield 102 for the electron discharge tube 104. As in the modification described hereinbefore, this tube includes a plate element 106, a control grid 108, a cathode 110 and a filament 112.

The cathode is connected to the enlarged section 98 of the tubing through the parallel combination of resistance 114 and capacitance 116, as indicated, and the control grid of each tube is connected to a central point on the caps 84, 86 of the outer shell. The filament is connected at one end to the tubing 98 through coil 118 and at the opposite end to filament lead 120. The plate element of the tube is connected through the primary winding 122 of a variable transformer to the plate voltage lead 124. This primary winding is connected to the enlarged portion of the tubing through a capacitor 116. The transformer is rendered adjustable by screwdriver adjustment of the core 128, in manner well known in the art. Access for the screwdriver is provided through openings 130, 132 in the outer shell and inner tubing, respectively, as indicated. The secondary winding 134 of the transformer is connected to a 72 ohm coax line 136 for connection to the input of a receiver. The leads 120, 124 and 136 are enclosed in a woven metal shield 13S which extends through and in electrical contact with tubing 94 and is secured electrically to the inner surface of the support 90 at the longitudinal center of the latter. as by solder connections 140. It is understood that the leads and shield are provided in suicient length to permit longitudinal adjustment of the outer shells.

In constructing the antenna illustrated in Figures 3, 4 and 5, a 6AN4 amplifier tube was modified to bring the control grid lead through the top of the envelope. The resistance 114 was 90 ohms, the capacitor 116 was 110 mmf., and the capacitor 126 was 500 mmf. Filament voltage was 6.3 volts and plate voltage was 200 volts. As in the operation of the antenna illustrated in Figure l, snow-free pictures and undistorted sound were obtained on VHF channels at a distance of about miles from point of broadcast.

It will be apparent to those skilled in the art that various changes in details of construction described hereinbefore may be made without departing from the scope and spirit of this invention. For example, the amplifier tubes illustrated may be replaced by transistors, if desired. The shape, size and values of components may be varied to accommodate desired conditions of construction and operation. Accordingly, it it to be understood that the foregoing description is primarily illustrative of the invention and is not to be considered as limiting the scope thereof.

Having now described my invention and the manner in which the same may be used, what I claim as new and desire to secure by Letters Patent is:

1. A receiving antenna comprising a hollow elongated electrically continuous signal receiving element including closed ends and having at least one end point of substantially maximum signal strength, signal amplification means contained within the hollow-signal receiving element and having plate and control grid elements, means connecting the control grid element to said end point of substantially maximum signal strength, means connecting the plate element to a source of operating potential, and tuned circuit means contained within the hollow-signal receiving element and associated with the plate element for connecting the output of the plate element to the input of a remotely positioned receiver.

2. A receiving antenna comprising a hollow elongated electrically continuous signal receiving element including closed ends each having a point of substantially maximum signal strength, a pair of signal amplification means contained within hollow signal receiving element and each having plate and control grid elements, means connecting each control grid element to one of said end points of substantially maximum signal strength, means connecting each plate element to a source of operating potential, and tuned circuit means contained within hollow signal receiving element and associated with each plate element for connecting the output of the latter to the input of a remotely positioned receiver.

3. The receiving antenna of claim 2 wherein each tuned circuit means comprises a coax cavity member, a tuned rod mounted within said cavity member and connecting the plate element to its source of operating potential, and a pickup loop member mounted within the cavity member adjacent said tuned rod and adapted for connection to the input of a receiver.

4. The receiving antenna of claim 2 wherein each tuned circuit means comprises a transformer having a primary winding interconnecting the plate element and its source of operating potential, and a secondary winding adapted for connection to the input of a receiver.

5. A receiving antenna comprising an elongated longitudinally adjustable hollow electrically continuous signal receiving element including longitudinally spaced ends each having a point of substantially maximum signal strength, a pair of signal amplification means contained within the hollow signal receiving element and each having plate and control grid elements, means connecting each control grid element to one of said end points of substantially maximum signal strength, means connecting each plate element to a source of operating potential, and adjustable tuned circuit contained within the hollow signal receiving element and means associated with each plate element for connecting the output of the latter to the input of a remotely positioned receiver.

6. The receiving antenna of claim 5 wherein each tuned circuit means comprises a coax cavity member, an adjustable tuned rod mounted within said cavity member and References Cited in the le of this patent UNITED STATES PATENTS Shumard July 31, 1934 Hollmann Aug. 15, 1939 Roberts July 16, 1946 Bridges et al. July 5, 1955 Bowers Mar. 25, 1958 Bredall Feb. 3, 1959 

